Hevacomp Netsys Ductwork Pressure Drop Calculation

Question

Dear Hevacomp Technical Support Team, 
 
 We understand that Hevacomp Ductwork Pressure Drop Calculation based their calculation as described in section C of CIBSE Guide but recently noticed that it is in edition 2001. We already have updated data on CIBSE Guide C as per edition 2007. This will cause big problem to us as there is an updates on K values of duct fittings between two CIBSE Guide version. Do we have a way to load the updated K value (CIBSE Guide C 2007) into the software so we can recalculate and come up with more realistic output? Is there a way to edit the K value in the data bank in Hevacomp? Can we edit manually the Kvalue of the autogenerated fittings in Hevacomp netsys? 
 
 Excerpt from Hevacomp Manual

We excerpt images from each version of CIBSE a K value of rectangular short bend duct to show a big discrepancy between two. Note that this is a sample only, other type of fittings have the same issue as well. 
 
 Excerpt from CIBSE Guide C 2001 for short bend

Excerpt from CIBSE Guide 2007 K vale for short bend

It seems that the K value is bigger in edition 2001 for hard bend and smaller K value for easy bend. This will have a big impact on the pressure loss result. 
 
 As of the moment we want to clarify the below. 
 
 If we add a user defined fitting (to setup the K value as described in CIBSE Guide C 2007) to an autogenerated fittings (like elbow and tees), will this overide the pressure drop of existing fittings? or both will be included in the calculation?

This is something urgent/important so we appreciate your prompt responds on this matter. 
 
 Godspeed,

Shane Regan · Answer

Hi Jovannie, the user defined fitting will be in addition to the bend, it will not override it. Unfortunately there is no way of manually editing the K-values in the software for the automatic bends tees and fittings.